The main causative factor of desertification is

Options

A. (a) overgrazing
B. (b) human Developmental activities
C. (c) irrigated agriculture
D. (d) tourism

Answer

### Step-by-Step Solution:

1. **Understanding Desertification**:
- Desertification refers to the process where fertile land becomes increasingly arid and unproductive, eventually turning into desert. This process can be caused by various factors, primarily related to soil health and vegetation cover.

2. **Identifying the Main Cause**:
- The primary cause of desertification is soil erosion. When the topsoil, which is rich in nutrients and supports plant life, is eroded, the land becomes barren.

3. **Role of Vegetation**:
- Vegetation plays a crucial role in preventing soil erosion. The roots of plants bind the soil together, protecting it from being washed away by rain or blown away by wind. Without this plant cover, the soil is exposed and vulnerable.

4. **Human Activities Contributing to Desertification**:
- Several human activities can lead to desertification, including:
- **Overgrazing**: When livestock graze excessively on land, they can strip away the vegetation, leading to soil exposure and erosion.
- **Deforestation**: Cutting down trees reduces the protective cover of the soil.
- **Urbanization**: Expanding cities can lead to the destruction of fertile land.
- **Over-irrigation**: Excessive irrigation can lead to salinization of the soil, making it infertile.

5. **Evaluating the Options**:
- Given the options:
- **A. Overgrazing**: This is a significant factor but not the only one.
- **B. Human Developmental Activities**: This encompasses overgrazing, deforestation, and other human actions that contribute to desertification.
- **C. Irrigated Agriculture**: While it can contribute, it is part of broader human activities.
- **D. Tourism**: This is not a primary factor in desertification.

6. **Conclusion**:
- The most comprehensive answer that includes various contributing factors is **B. Human Developmental Activities**. This option covers multiple aspects that lead to desertification, making it the best choice.

### Final Answer:
The main causative factor of desertification is **B. Human Developmental Activities**.